Changing water pressure on house pressure regulator.

I have an old inline whole house pressure regulator. My city water pressure is around 85 pounds. I have tried to adjust the regulator with a gauge attached right after the regulator with no change in pressure at gauge. 2 questions......the regulator is about 20 years old....is it possible that it is not working.......and what is the proper procedure for adjusting the pressure on the regulator? The regulator is a Watts....thanks

The procedure is to make a couple of turns on the screw ( CW to increase pressure), then open a tap to allow flow for several seconds to allow the regulator to "settle". Then close the tap and see what the new pressure is.

Are you trying to increase or decrease pressure? It would frankly be surprising if a 20 year old regulator is still working at all!

You should be able to RAISE the pressure without opening a faucet, but you cannot lower it without relieving the pressure somehow so you can tell what your adjustment is doing. IF the "adjusted" pressure is the same as the "raw" pressure the valve is not working.